This invention relates to a sensor for controlling the operation of a pump to maintain the pressure level of a fluid in a reservoir within a predetermined pressure range.
Diesel and turbine powered engines do not produce a vacuum such as developed by an internal combustion engine. Unfortunately, many accessories on conventional vehicles are operated by a pressure differential created between air in the surrounding environment and vacuum. Rather than modify the operation of such vacuum operated accessories it has proven more economical to equip diesel and turbine powered vehicles with a vacuum pump and storage reservoir. Such vacuum pumps normally operate all the time that the diesel or turbine engine is running. Studies have shown that under normal and average driving conditions the vacuum pump need only operate about 10% of the time to meet the requirement of the accessories. Thus, it should be evident that a control capable of turning the pump on and off as needed to operate the accessories could result in energy savings while at the same time prolonging the life of the pump. Unfortunately, the differential pressure at which the pump turns on or off must closely match the pump's capability, while the differential pressure that a pump is capable of generating is a function of air density and temperature in addition to the normal factors such as efficiency, wear, etc.